PORTLAND, Maine — The voters of Portland will decide on June 10 whether they want the chance to decide — through a second vote — if part of the publicly owned Congress Square Park should be sold to a private hotel developer.

In a largely procedural move, the City Council on Monday night unanimously voted to place a referendum on the ballot amending the city’s Land Bank Commission ordinance as demanded in a petition circulated by citizens’ groups opposed to the controversial Congress Square sale.

In what has become somewhat of a chess game between opponents of the sale and city officials seeking to make the deal final, the council also voted to refer a competing ordinance change to a future workshop setting, where it will survive to a later date.

The alternative ordinance being pushed by the council would provide added protections for public spaces like the petitioners’ proposal, but would allow the Congress Square sale to go through.

The council could have decided Monday night to put that competing measure on the June 10 ballot as well, giving voters multiple choices at the booth. The council did not, however, and by punting the alternate ordinance to a future workshop for further review, it will re-emerge at the council level in April.

The council voted 7-2 to move its ordinance to a workshop later this month, with councilors Kevin Donoghue and David Marshall opposed.

The council on Monday night also could have enacted the petitioners’ ordinance outright, then amended it after 30 days to be more accommodating to the Congress Square sale, as suggested by Portland Community Chamber consultant Christopher O’Neil. The council instead voted unanimously to postpone enacting the petitioners’ ordinance indefinitely before choosing to put it on the June ballot.

The council’s alternative ordinance is meant in part to convince any fence-straddling Portland voters that the petitioners’ proposed ordinance change isn’t necessary. If the city’s competing ordinance lands on the books before June 10, it could be used as part of a city argument against the more stringent referendum on the ballot.

“Portland voters will see it for what it is, which is an attempt to undermine the true parks initiative that we’ve put forward,” Rob Levin, an attorney representing one of the petitioning groups, told the council Monday. “I see this alternative as ‘Parks Light.’”

The petitioners’ proposal, if passed, would change the Land Bank Commission ordinance to include Congress Square Park and 34 other city properties not currently protected. It would further require a citywide vote to approve the sale of any of the land bank properties — unless a supermajority of the City Council, or eight of the nine members, votes to sell.

The council’s competing draft protects many of the other properties, but leaves Congress Square off the list, and allows the council to sell the protected spaces with seven councilor votes, instead of the eight-vote council threshold included in the petitioners’ version.

The petitioners turned in more than 4,250 signatures to the city clerk’s office asking for the ordinance change, a number nearly three times the 1,500 names necessary to force the proposal’s outright adoption or a citywide vote.

The city of Portland only turned over petition papers after being ordered to do so by a Cumberland County Superior Court judge last fall, and is now appealing that decision to the Maine Supreme Judicial Court.

In its appeal, which was filed last month, the city reiterated its arguments that the citizens petition process is reserved for legislative changes, but that affecting the disposition of city property improperly crosses the line into being an administrative or fiscal action.

Deciding on city appropriations — a term which Portland Corporation Counsel Danielle West-Chuhta argued could be used to apply to property as well as money — is “exclusively within the province of the City Council,” she wrote in the appeal.

In this case, the council voted 6-3 in September to sell nearly 9,500 square feet of the plaza for nearly $524,000 to Ohio-based private developers RockBridge Capital LLC. RockBridge helped finance the nearly $50 million renovation of the historic former Eastland Park Hotel nearby and hopes to use the additional Congress Square space for an event center.

If the petitioners’ ordinance change is ultimately approved at the polls, it would trigger a second citywide vote to retroactively vet the council’s September decision to sell most of Congress Square Park.

Proponents of the sale, including the Portland Community Chamber, have argued that Congress Square is dangerously close to being a vacant space, and that with the sale, it will go from an underutilized section of pavement to a more vibrant commercial spot.

But opponents have said it’s the city’s responsibility to fix up the park, not just give up ownership.